1. Field of the Invention
The invention relates to an energy absorption device for a railborne vehicle, in particular a streetcar vehicle, wherein the energy absorption device is designed so as to absorb or dissipate at least part of the impact energy which occurs when the vehicle impacts an obstacle. The invention moreover relates to a shock absorber for the front or rear region of a railborne vehicle, in particular a streetcar vehicle, wherein the shock absorber includes at least one energy absorption device as noted above which is connectable to the vehicle underframe at the front or rear region of the vehicle.
2. Description of the Related Art
It is known to equip railborne vehicles such as track-borne vehicles, for example, with a shock absorber including at least one energy absorption device which serves to at least partly dissipate the impact force which occurs when the vehicle impacts an obstacle. An energy absorption device used in a shock absorber usually includes one or more energy-absorbing mechanisms. Destructively-designed energy-absorbing mechanisms have the function of protecting the underframe of the railborne vehicle, in particular also at high collision speeds.
Additionally to the at least one destructively-designed energy-absorbing mechanism, a regeneratively-designed energy-absorbing mechanism can be further provided, which usually serves to cushion the impact forces occurring during normal vehicle operation.
In conventional shock absorbers, the regeneratively-designed energy-absorbing mechanism is designed so as to cushion the tractive and impact forces occurring during the normal operation of the vehicle, wherein the damping capacity of the regeneratively-designed energy-absorbing mechanism is often only dimensioned up to a fixed maximum force. In other words, after the operating load of the regeneratively-designed energy-absorbing mechanism is exceeded, for instance when the vehicle impacts an obstacle (i.e., a crash), the regeneratively-designed energy-absorbing mechanism is usually too limited to absorb the full amount of resultant impact energy.
So that the resultant impact energy will preferably not lead to high loads in such a case, in addition to the regeneratively-designed energy-absorbing mechanism, a destructively-designed energy-absorbing mechanism is for example provided downstream the regeneratively-designed energy-absorbing mechanism and designed so as to respond after the working absorption of the regeneratively-designed energy-absorbing mechanism has been exhausted and then absorb and dissipate at least some of the energy transferred in the force flow through the energy absorption device.
Conceivable as destructively-designed energy-absorbing mechanisms would, for example, be deformation tubes or crash boxes with which impact energy can be converted into the work of deformation and heat by a defined destructive deformation. A deformation tube used in a shock absorber as a destructively-designed energy-absorbing mechanism is characterized for example by exhibiting a defined activation force with no spikes in the force.
Buffers having a regenerative or self-restoring mode of operation, such as e.g., gas-hydraulic buffers, are known as regeneratively-designed energy-absorbing mechanisms. An energy-absorbing mechanism based on gas-hydraulic operation has a relatively low activation force compared to a deformation tube and exhibits—unlike a deformation tube—a speed-dependent response. On the other hand, energy-absorbing mechanisms based on hydrostatic operation such as e.g. a gas-hydraulic buffer, are also known as regeneratively-designed energy-absorbing mechanisms, same likewise functioning regeneratively, i.e., self-restoring. Compared to gas-hydraulic energy-absorbing mechanisms, hydrostatic energy-absorbing mechanisms have a higher activation force and initial load.
It has long been endeavored in rail vehicle technology to provide a shock absorber to protect the underframe of a railborne vehicle from extreme loads occurring in particular upon a crash with which at least a portion of the impact energy occurring during the transmitting of impact forces, for example upon a crash, can be effectively dissipated in a defined manner and pursuant a predictable sequence of events. It is necessary, both for a defined response as well as for a predefinable sequence of events when absorbing energy, for the impact force which is to be cushioned, and thus, the energy resulting from the transmitting of the impact force, to be introduced in as axial a manner as possible in the energy-absorbing mechanism(s) of the energy absorption device(s) provided in the shock absorber. This can be attributed to the fact that an energy absorption device normally employed in a shock absorber comprises an energy-absorbing mechanism such as, for example, a deformation tube or a crash box, whereby this energy-absorbing mechanism can usually only absorb forces in a predictable manner when they are introduced axially into the energy-absorbing mechanism.
For example, should a deformation tube or a crash box be employed as an energy-absorbing mechanism, there is the risk—when non-axial forces are introduced into the deformation tube—of “seizing” or wedging and canting, with the result that the response of the energy-absorbing mechanism on the one hand and the sequence of events during energy absorption on the other are no longer predictable.
These basic conditions for the effective functioning of an energy-absorbing mechanism are often inherent in the case of railborne vehicles such as e.g., streetcar vehicles, since a rail vehicle moving along a rail line, such as a regional transit train or a high-speed train, usually always comes upon an obstacle situated on the rail line from the frontal direction so that also when colliding with the obstacle, the resultant impact energy is introduced axially to the energy-absorbing mechanism of the energy absorption device provided in the shock absorber quasi “automatically,” since the preferred direction of the energy absorption mechanism during energy absorption normally coincides with the longitudinal direction of the rail vehicle.
Streetcars, for example, however, represent a special case; i.e., railborne and specifically track-borne vehicles which are at least partly incorporated into normal road traffic. With these types of vehicles, the basic condition, according to which a collision with an obstacle is usually frontal, is no longer automatically met. If, for example, an automobile attempting to turn in traffic collides with an oncoming streetcar, it will often not collide with it frontally, but rather at an oblique side-on angle to the front. In such situations, in no way can this be deemed a frontal or substantially frontal collision.
Therefore, the problem on which the invention is based is that in terms of absorbing the impact energy which occurs upon a crash, the conventional solutions, for example known in rail vehicle technology and already effectively employed in regional transit or high-speed trains, are not or are at least not sufficiently suited to absorb or dissipate the impact energy occurring upon a non-axial and in particular side-on collision of the vehicle with an obstacle; i.e., pursuant a predictable sequence of events.
Given this problem as defined, the invention is thus, based on the task of further developing an energy absorption device of the type cited at the outset such that it can also absorb or dissipate the impact energy occurring upon a side-on collision of the vehicle with an obstacle according to a predefinable sequence of events.